>>>>I've frequently tried to make the point that all the scaling for>>>>lots of processors is nonsense. Mr Dell says it better:>>>>>>>> "Eight-way (servers) are less than 1 percent of the market and>>>> shrinking pretty dramatically," Dell said. "If our competitors>>>> want to claim they're No. 1 in eight-ways, that's fine. We>>>> want to lead the market with two-way and four-way (processor>>>> machines).">>>>>>>>Tell me again that it is a good idea to screw up uniprocessor>>>>performance for 64 way machines. Great idea, that. Go Dinosaurs!>>>>>>>And does your 4 way have hyperthreading?>>>>>What part of "shrinking pretty dramatically" did you not understand?>>Maybe you know more than Mike Dell. Could you share that insight?>>>>Ok. But only because you asked nicely.>>Mike Dell wants to sell 2 and 4 processor boxes and Intel wants to sell >processors with hyperthreading on them. Scaling to 4 or 8 threads is just>like scaling to 4 or 8 processors, only worse.>>However, lets not end up in a yet another 64 way scalability argument here.>>The thing we should be worrying about is the UP -> 2 way SMP scalability>issue. If every chip in the future has hyperthreading then all of sudden>everyone is running an SMP kernel. And what hurts us?>>atomic ops>memory barriers>>Ive always worried about those atomic ops that only appear in an SMP>kernel, but Rusty recently reminded me its the same story for most of the>memory barriers.>>Things like RCU can do a lot for this UP -> 2 way SMP issue. The fact it>also helps the big end of town is just a bonus.>

I think LM advocates aiming single image scalability at or before the kneeof the CPU vs performance curve. Say thats 4 way, it means you should getgood performance on 8 ways while keeping top performance on 1 and 2 and 4ways. (Sorry if I mis-represent your position).

I don't think anyone advocates sacrificing UP performance for 32 ways, butas he says it can happen .1% at a time.

But it looks like 2.6 will scale well to 16 way and higher. I wonder ifthere are many regressions from 2.4 or 2.2 on small systems.